Low-density dynamite



Patented oct. 12, 1926.

UNITED STATES PATENT OFFICE.

WENDELL R. SWINT, OF LONDON, ENGLAND, ASSIG-NOR TOE; I. DU PONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

LOW-DENSITY DYNAMITE.

No Drawing.

This invention relates'to the manufacture of explosives having av liquid sensitizing agent. and in particular to the manufacture of ammonium nitrate explosives of the permissible type.

In the mining of coal. it is at times important to obtain the maximum possible proportion of lump product. For the production of this type of product. it has become recognized that for economy in operation, the strongest possible explosive must be used. having at the same time the lowest possible velocity. and a density such as to give the proper distribution of explosive in the bore hole. With these properties must of course be coupled permissibility for use in coal mines. and suff cient sensitiveness to detonation to insure propagation of explosion throughout a single charge.

In the development of this type of explosive. the disclosures of Woodburr (U. SP.- 1,113.27 5 and 1.124.679) brought about a great step forward. By his method, the velocity of detonation is lowered by increasin the size of the granules of the nitrate of ammonia. the reduction in velocity being in general proportional to the increase in the size of the granules. This method of con trol of velocity has had definite limitations in that the use of a too coarsely granulated nitrate oi ammonia will tend to interfere with the strength of the explosive. and with the known absorbents it has been diflicult to obtain any material reduction in density (with consequent reduction in velocity) beyond certain rather definite limits Without interfering seriously with the sensitiveness ot the dynamite.

Explosives ot the type described above have previously been made of such a density that a 1%x8 cartridge has weighed 160 to 180 grams (126 to 1&2 sticks per lbs), and have in general been made with ammonium nitrate of such fineness that the major portion of the grains pass a 10 mesh, and are held on a mesh screen. Ammonium nitrate of this degree of subdivision may be referred to as a relatively coarse ammonium Application filed August 23, 1924. Serial No. 733,780.

nitrate. An example of such a composition follows Vood flour -r Cornmeal Y. Per cent hitroe'lycerme 1O Ammonium nitrate 80 Many variations have of course been made in torn'uilas of this type. as for example, the substitution of 320% sodium chloride for a corresponding proportion of the ammonium nitrate: the use of similar proportions of sodium nitrate in place of the ammonium nitrate: the substitution of other carbonaceous materials. such as starch, ivory nut meal, sawdust, wood pulp, tor the wood flour and cornmeal and the use of other explosive liqu ds as substitutes for all or part of the mtroglycerme; as well as various changes gredients mentioned.

in the relative proportions of the several in- Using previously known materials andrelativelv coarse ammonium nitrate such as is described above. the lowest density it has been previously possible to obtain in explosives of this type corresponds to a weight of about 151 grams (150 sticks per 50 lbs.) in 1%x8 cartridges. and this can be obtained only by the greatest care in the prepa ration and selection of materials.

The explosives manufactured from this type of coarse ammonium nitrate have in general had velocities below 2500 m/sec. In order to obtain lower densities than this, it has been necessary to use finer nitrate of ammonia, which in turn has caused an undesirable increase in velocity.

reduction in density obtained.

. My new absorbent is obtained by the treatment of sugar cane in such a way as to recover the so-called bagasse pith. According to this treatment, the residue'from the sugar cane, after the extraction of the sugar, said residue usually being in a' crushed and macerated condition, is screened to remove themajority of the long fibers, leaving mainly the pith. Small ercentages of the fibers do not interfere wit securing the desired results, but the pith as used in my invention should preferably not contain over fiber. Other methods of sugar manufacture in which the entire cane is first shredded and dried and then extracted with water to remove the sugar also may be utilized in obtainingbagasse pith of properties which are satisfactory for use in my invention.

The product thus obtained is a finely divided material having a distinct cellular structure, with very distinctive appearance when viewed under the microscope.

V I may use this absorbent either as a partial or complete substituent for the carbonaceous materials previously used. For example, the following table shows one series of formulas illustrating the use of the new absorbent, though it is to be understood that the formulas here given constitute only a small proportion of the possible formulas in which the material can be used.

Per cent.

Per cent.

- Per cent.

The decrease in density obtained in the finished dynamite will of course vary with the extent to which the substitution of the new absorbent is carried. I have been able with such formulas to obtain average densities corresponding to as low a welght as 125 grams (181 sticks per case) for an 1%x8" cartridge without seriously aifecting the sensitiveness of the explosive. Considerably lower densities than this can be obtained by increasing the content of bagasse pith absorbent beyond the amount used in the aboveformulas. This change however mustusually be accompanied by slight increases in nitroglycerine content in'order that sensitiveness may be maintained, and this in turn will in certain cases necessitate the inclusion of additional safety ingredients,

for example N aOl or NH,,C1, replacing for example part of the ammonium nitrate.

The most im ortant ranges in composition which are possible may be indicated as follows Per cent. Nitroglycerine 7-15 Relatively coarse ammonium nitrate 40-85 Sodium'nitrate 0-20 Sodium chloride 0-20 Bagasse pith 3-15 It. is understood that there maybe substituted other liquid explosive materials for part or all of the nitroglycerine; for example, tetranitrodiglycerine or ethylene glycol dinitrate that there may be used any of the well recognized methods for depressing the flame temperature in order to obtain an explosive permissible for use in coal mines, and that there may be used bagasse pith either alone or in conjunction with other carbonaceous materials without departing from the invention.

' I claim:

1. A dynamite comprising relatively coarse ammonium nitrate, bagasse pith and a liquid explosive ingredient, having a density such that an 1%"x8 cartridge will weigh less than 146 grams, and having a velocity less than 2500 m/sec.

2. A low velocity dynamite. comprising to 80 per cent of relatively coarse ammonlum nitrate, bagasse pith and a liquid explosive ingredient, and having a density such that an 1%"x8" cartridge will weigh less than 146 grams. 5

3. A low velocity dynamite comprising 50 to 80% relatively coarse ammonium nitrate, bagasse pith and 7 to 15% of a liquid explosive ingredient, and having a density such that an 1%"x8" cartridge will weigh less than 146 grams.

4. A low velocity dynamite comprising relatively coarse ammonium nitrate, a liquid explosive ingredient and bagasse pith. --5. A low velocity dynamite comprising relatively coarse ammonlum nitrate, nitroglycerine, and bagasse pith. I

6. n ammonium nitrate dynamite of a velocity less than 2500 m/sec., the velocity being reduced by the incorporation of the ammonium nitrate in the form of coarse crylsltals and also by the presence of bagasse plt v In testimony whereof aflix my signature.

' WENDELL R. SWINT. 

